1. Field of the Invention
The present invention relates to communication systems, and more particularly, to a method and apparatus for operating a network switch without the use of a CPU.
2. Description of the Related Art
Modern communication systems, such as computer networking systems or communication networks, provide constant transmission of data between end stations and/or intermediate stations such as routers and signal amplifiers. Computer networking systems, such as packet switched networks (e.g., Ethernet networks), often require transmission of data to a single end station or to multiple end stations within the network. The data originates from a user program, and is segmented into multiple data frames and subsequently transmitted in order to simplify processing and minimize the retransmission time required for error recovery. For example, in a conventional e-mail system, a user may desire to send the same e-mail message to four different users that are connected to the e-mail system. Accordingly, the identical data would be directed to multiple end stations.
Packet switched computer networks typically employ a network switch that receives and forwards data frames to individual and/or multiple end stations. The switch makes forwarding decisions upon receipt of the data frames based on information contained in a header of each data frame. For example, if a received data frame is to be transmitted to a number of end stations, the switch must make the forwarding decision to forward the data frame to the ports of the correct end stations. Prior to engaging in routine network activity, however, it is necessary to properly initialize and configure the network switch in order to enable transmission of data frames between the various stations.
Initialization and configuration of the network switch are typically accomplished by a host microprocessor, i.e., a Central Processing Unit, (or CPU) that configures and controls the network switch prior to, and during runtime. Microprocessors, however, can be relatively costly and require substantial hardware and software resources to support basic operations. For example, microprocessor implementations may require reserved storage space in a read-only memory (ROM) in order to store the instruction sets and operating system code necessary for execution of the control functions that interface the microprocessor to the network switch. Microprocessors additionally require non-volatile random access memory (RAM) devices for storing routines that control operation of the network switch. Additional interface devices may also be necessary for controlling data transfer between the host microprocessor and the network switch. Finally, the host microprocessor is often responsible for controlling and monitoring numerous functions that are unrelated to operation of the network switch. Consequently, an unnecessary delay is caused when the microprocessor is also responsible for management and control of the network switch. This delay is particularly apparent at startup when the microprocessor must initialize various devices prior to initializing the network switch.
Accordingly, a principal problem associated with network switches that must be controlled or initialized by a microprocessor is the delay that results when the microprocessor must also control various devices other than the network switch.
Another problem associated with network switches that must be controlled by a microprocessor is the cost and complexity associated with incorporating circuitry to interface the microprocessor to interact with the network switch.
There exists a need for an arrangement capable of quickly and efficiently initializing and configuring a multiport network switch without the use of a microprocessor.
These and other needs are addressed by the present invention wherein a multiport switch that receives data frames includes circuitry for forwarding the received data frames to one or more output ports thereof, without the use of a microprocessor.
In accordance with one aspect of the present invention, a method of operating a multiport switch in a CPU-less interconnect environment comprises the steps: transmitting an initialization signal from a control interface, used to connect the multiport switch and a CPU, to an internal rules checker that decides which one or more output ports of the multiport switch will output received data frames; transmitting a ready signal to the control interface to indicate that the internal rules checker is initialized; enabling the multiport switch; and forwarding received data frames to the one or more output ports of the multiport switch, based on a source address and a destination address stored in a header of each received data frame. The present method provides a low-cost arrangement for initializing and configuring a multiport switch without the use of a microprocessor. Hence, the multiport switch can be easily initialized while the microprocessor attends to the initialization of other components of its host station. One advantage of such an arrangement is the minimization of the down-time experienced before the multiport switch is operational.
In accordance with another aspect of the present invention, an apparatus is provided for operating a multiport switch in a CPU-less environment. The apparatus includes a control interface and an internal rules checker. The control interface is configured for connecting an external CPU to the multiport switch. The control interface generates an initialization signal upon detecting the absence of the CPU at start-up. The initialization signal is received by the internal rules checker which, in turn, initializes the multiport switch to receive and forward data frames to appropriate output ports. The internal rules checker then forwards data frames to the output ports based on a sending address and destination address contained in the header of each received data frame. According to the present invention the amount of time required to initialize the network switch at start-up can be reduced, while simultaneously reducing the cost of operation because no CPU is required.
Additional advantages and novel features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.